Novel in vivo Assessment of Unruptured Intracranial Aneurysm Inflammatory Factors

Background and Purpose: The growth and eventual rupture of intracranial aneurysms may be due to an underlying inflammatory process as evidenced by pathological examination of aneurysm walls. We hypothesize that unruptured aneurysms have an increased inflammatory milieu within their lumen in comparison to the rest of the cerebral arterial vascular system.

Methods: Blood was sampled from unruptured aneurysms in patients presenting for aneurysm coil embolization and C3 and C4 complement values from this serum were compared with complement values in the parent artery.

Results: Ten patients were enrolled over 32 months with a mean aneurysm size of 9.1 mm. Compared to control samples drawn from peripheral circulation, there were significant decreases of both C3 (p = 0.0003) and C4 (p = 0.0063) levels in aneurysmal blood samples.

Conclusions: A state of decreased complement indicative of classic pathway activation was found in all tested aneurysms, thus providing evidence of an ongoing process of complement activation in the blood of live, unruptured aneurysm sacs.

Neuronal Entropy-Rate Feature of Entopeduncular Nucleus in Rat Model of Parkinson's Disease

The function of the nigro-striatal pathway on neuronal entropy in the basal ganglia (BG) output nucleus, i.e. the entopeduncular nucleus (EPN) was investigated in the unilaterally 6-hyroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD). In both control subjects and subjects with 6-OHDA lesion of dopamine (DA) the nigro-striatal pathway, a histological hallmark for parkinsonism, neuronal entropy in EPN was maximal in neurons with firing rates ranging between 15 and 25 Hz. In 6-OHDA lesioned rats, neuronal entropy in the EPN was specifically higher in neurons with firing rates above 25 Hz. Our data establishes that the nigro-striatal pathway controls neuronal entropy in motor circuitry and that the parkinsonian condition is associated with abnormal relationship between firing rate and neuronal entropy in BG output nuclei. The neuronal firing rates and entropy relationship provide putative relevant electrophysiological information to investigate the sensory-motor processing in normal condition and conditions such as movement disorders.

Abstract W MP46: Novel In Vivo Assessment of Unruptured Intracranial Aneurysm Inflammatory Factors: Prospective Analysis of Intra-Aneurysmal Serum Inflammatory Markers in a University Hospital

Background: There are known correlations between intracranial aneurysm size as well as underlying demographic risk factors that lead to aneurysm rupture. The treatment of unruptured aneurysms is predicated on this, however selecting which unruptured aneurysms should be treated can be difficult. It is thought that formation, growth and eventual rupture of aneurysms is due to an underlying inflammatory process, which has been shown in pathological studies to exist within aneurysmal walls. The inflammatory milieu within a live aneurysmal sac and its implications for aneurysmal rupture is not currently known.

Objective: To determine the presence of inflammatory markers within unruptured aneurysm sacs.

Methods: We analyzed prospectively collected data from a database of patients who presented for unruptured aneurysm coil embolization over the span of 25 months to a University Hospital. These patients had blood samples withdrawn from the aneurysm sac immediately prior to coil embolization. This blood was sent for testing, with controls provided by blood sampled from the aneurysm parent vessel. Complement C3 and C4 levels from the aneurysm and parent vessel were then compared using column tables with paired t-test analysis.

Results: A total of 8 patients were enrolled. The mean age (± SD) of treated patients was 68 (±15.3) years and 7 (87.5%) were women. 5 aneurysms (62.5%) were in the anterior circulation. Aneurysm size ranged from 5mm to 14mm, mean size 8.9mm (± 3.1mm). 5 patients (62.5%) were white while 7 patients (87.5%) had history of hypertension. C3 and C4 analysis showed a consistent decrease of complement values within the aneurysm as compared to the parent vessel. (For C3, mean of differences [MD] was 9.375, 95% confidence interval [CI] 5.56-13.19. For C4, MD was 1.500, 95% CI 0.50-2.50.)

Conclusion: There is an observed decrease in complement values within unruptured aneurysms, suggestive of ongoing classic complement pathway activation. This supports the aneurysm inflammation model, which shows complement deposition in aneurysm walls. Our data suggests that this process is ongoing in live unruptured aneurysms and could be possibly targeted in future aneurysm trials. Further investigation is needed.

Using a virtual training program to train community neurologist on EEG reading skills

BACKGROUND

EEG training requires iterative exposure of different patterns with continuous feedback from the instructor. This training is traditionally acquired through a traditional fellowship program, but only 28% of neurologists in training plan to do a fellowship in EEG.

PURPOSE

The purpose of this study was to determine the value of online EEG training to improve EEG knowledge among general neurologists.

METHODS

The participants were general neurologists invited through bulk e-mail and paid a fee to enroll in the virtual EEG program. A 40-question pretest exam was performed before training. The training included 4 online learning units about basic EEG principles and 40 online clinical EEG tutorials. In addition there were weekly live teleconferences for Q&A sessions. At the end of the program, the participants were asked to complete a posttest exam.

RESULTS

Fifteen of 20 participants successfully completed the program and took both the pre- and posttest exams. All the subjects scored significantly higher in the posttest compared to their baseline score. The average score in the pretest evaluation was 61.7% and the posttest average was 87.8% (p = .0002, two-tailed).

CONCLUSIONS

Virtual EEG training can improve EEG knowledge among community neurologists.

Development of a therapeutics curriculum to enhance knowledge of fourth-year medical students about clinical uses and adverse effects of drugs

BACKGROUND

Enhanced clinical pharmacology and therapeutics education of medical students is important for improving effective and safe drug therapy. Increased education about pharmacovigilance is needed because serious drug-induced adverse effects are increasing. Fostering the needed scientific approach to prescribing requires knowledge of evidence-based drug therapy, based on understanding clinical trials. Therapeutic agents with novel mechanisms of action are increasingly available, and an unbiased understanding of the risks and benefits of novel agents is also important. These issues can be addressed in clinical pharmacology courses. However, many medical schools lack sufficient clinical pharmacologists to teach such courses. The Southern Illinois University Medical School faculty implemented an Advanced Therapeutics course to address these issues.

DESCRIPTION

Development of this course involved defining appropriate content and organizing preclinical pharmacology and clinical faculty into teaching teams. The course was offered to 4th-year medical students and covered clinical trial information, and cutting-edge therapeutic developments. The "ABCs of Pharmacology" is a mental algorithm that was presented in the sophomore year and reintroduced in this course. This algorithm emphasizes pharmacovigilance, which stresses the balance between positive and negative effects of pharmacological agents. General principles of clinical pharmacology and therapeutics were covered by a clinical pharmacologist. Most sessions on specific disease treatment involved an integrated presentation by a preclinical pharmacologist and a clinician with expertise in that topic, often in the context of clinical cases. Other important topics were emphasized, which reinforce individualization of therapy, including pharmacogenomics that may determine idiosyncratic responses. Feedback during and following the course was obtained via questionnaires.

EVALUATION

This approach was well received by participating students and graduates. Most students rated this course as a valuable experience.

CONCLUSION

This approach appears useful for educating medical students about therapeutics at medical schools that lack sufficient clinical pharmacology faculty to mount such a course.

Lamotrigine extended-release as adjunctive therapy for partial seizures

OBJECTIVE

To evaluate the efficacy and tolerability of once-daily adjunctive lamotrigine extended-release (XR) for partial seizures in epilepsy.

METHODS

Patients more than 12 years old diagnosed with epilepsy with partial seizures and taking one to two baseline antiepileptic drugs were randomized to adjunctive once-daily lamotrigine XR or placebo in a double-blind, parallel-group trial. The study comprised a baseline phase, a 7-week double-blind escalation phase, and a 12-week double-blind maintenance phase during which doses of study medication and concomitant antiepileptic drugs were maintained.

RESULTS

Of the 243 randomized patients, 239 (118 lamotrigine XR, 121 placebo) entered the escalation phase and received study medication. Lamotrigine XR was more effective than placebo with respect to median percent reduction from baseline in weekly partial seizure frequency (primary endpoint-entire 19-week treatment phase: 46.6% vs 24.5%, p = 0.0001 [corrected] via Wilcoxon test; escalation phase: 29.8% vs 15.6%, p = 0.027; maintenance phase: 58.4% vs 26.8%, p [corrected] < 0.0001). The percentage of patients with >or=50% reduction in partial seizure frequency (44.0% vs 20.8%, p = 0.0002) [corrected] and time to >or=50% reduction in partial seizure frequency (p = 0.0001) [corrected] also favored lamotrigine XR over placebo. A similar pattern of results was observed for secondarily generalized seizures. The most common adverse events were headache (lamotrigine XR 16%, placebo 18%) [corrected] and dizziness (lamotrigine XR 19%, [corrected] placebo 5%). Differences between lamotrigine XR and placebo on health outcomes measures were not significant.

CONCLUSIONS

Once-daily adjunctive lamotrigine extended-release compared with placebo effectively reduced partial seizure frequency and was well tolerated in this double-blind study. Results support the clinical utility of this new once-daily formulation.

Randomized dose-controlled study of topiramate as first-line therapy in epilepsy

OBJECTIVES

To evaluate the efficacy and tolerability of topiramate as monotherapy, using a dose-controlled study design.

MATERIALS AND METHODS

We conducted a multinational, randomized, double-blind trial in adults and children (> or =6 years old) with epilepsy that was not being treated when randomized to 400 or 50 mg/day topiramate as target maintenance dosages. In addition to > or =2 lifetime unprovoked seizures, patients had to have one or two partial-onset seizures or generalized-onset tonic-clonic seizures in the 3-month retrospective baseline. The primary efficacy end point was time to first seizure; a secondary efficacy measure was the seizure-free rate at 6 months and 1 year. Double-blind treatment continued until 6 months after the last patient was randomized.

RESULTS

Kaplan-Meier survival analyses for time to first seizure (intent-to-treat, n = 470) favored 400 mg/day over 50 mg/day (P = 0.0002) as a target maintenance dosage. The first evaluation point with a significant difference (P = 0.046) favoring the higher dose was at day 14 when patients were receiving 100 or 25 mg/day. The probability of being seizure-free at 6 months was 83% in patients randomized to 400 mg/day and 71% in those randomized to 50 mg/day (P = 0.005). Seizure-free rates at 12 months were 76% and 59%, respectively (P = 0.001). Differences favoring the higher dose were significant in patients with partial-onset seizures (P = 0.009) and in those with generalized-onset tonic-clonic seizures (P = 0.005). The most common dose-related adverse events were paresthesia, weight loss, and decreased appetite. Discontinuations due to cognitive-related adverse events were 2% in the 50-mg group and 7% in the 400-mg group. Overall, 7% and 19%, respectively, discontinued with adverse events during the median treatment duration of 9 months.

CONCLUSION

Topiramate is effective as monotherapy in adults and children. Because a therapeutic effect emerges during titration, clinicians should adjust dosages in step-wise fashion with intermediate stopping points, e.g., 100 mg/day, to evaluate patient response and achieve the optimal maintenance dosage.

Metabolic changes in rat striatum following convulsive seizures

Generalized convulsive seizures increase glucose utilization within the brain but their impact on metabolism is not well known. The striatum receives excitatory input from widespread sources in the brain and could potentially reflect energy depletion in the brain resulting from generalized seizures. We utilized multiprobe microdialysis in freely moving rats subjected to maximal electroshock to simultaneously measure glucose, lactate, and pyruvate levels in the interstitial space within striatum and in peripheral subcutaneous tissue. A brief convulsive seizure was associated with marked changes in striatal and peripheral metabolism during the post-ictal state that lasted up to 1 h. There were significant central and peripheral elevations of glucose, pyruvate, and lactate, reflecting increased glucose metabolism. Interestingly, the lactate-to-pyruvate ratio increased significantly in the periphery but remained unchanged in the striatum. Thus, there appears to be brain mechanisms that maintain adequate energy sources and prevent anaerobic shift during the post-ictal state.

Effect of cotherapy reduction on tolerability of epilepsy add-on therapy: a randomized controlled trial

BACKGROUND

Adverse effects are the most common cause for failure of an antiepileptic drug (AED), especially when an AED is added to existing therapy. With the increased drug load, it may not be possible to titrate the newly added AED to effective doses. Reducing the dosage of AED cotherapy as the new drug is introduced may improve tolerability.

OBJECTIVE

To evaluate reduction of AED cotherapy as a strategy to improve tolerability and patient retention when a new AED is added to existing therapy.

METHODS

In a 20-week, randomized, open-label study, topiramate was initiated as add-on therapy in adults and adolescents (> or =12 y of age) with inadequately controlled partial-onset seizures. Patients were randomized to receive treatment in which adverse events could be managed by adjustments in AED cotherapy (flex-dose group) or treatment in which AED cotherapy dosages remained fixed (fixed-dose group). Topiramate could be adjusted as needed in both groups. In the flex-dose group, patients exited randomized treatment when topiramate was discontinued. In the fixed-dose group, patients exited when AED cotherapy was reduced due to adverse events or when topiramate was discontinued. The primary study outcome was the percentage of patients exiting randomized treatment due to adverse events.

RESULTS

The flex-dose group comprised 297 patients; 302 patients were in the fixed-dose group. Significantly fewer patients in the flex-dose group exited the study due to adverse events (16% vs 23% in the fixed-dose group; p = 0.02). In the flex-dose group, 10% (17 of 168) of patients discontinued topiramate due to adverse events after AED cotherapy was reduced versus 22% (29 of 129) when AED cotherapy was not reduced.

CONCLUSIONS

Reduction of AED cotherapy is a useful strategy to improve tolerability and retention when topiramate is initiated as adjunctive therapy.

Intraoperative human vagus nerve compound action potentials

OBJECTIVE

Although electrical stimulation of vagus nerve is used widely for treatment of epilepsy the electrophysiological properties of human vagus nerve are not well characterized. Our objective was to measure compound action potentials of human vagus nerve fiber groups intraoperatively by stimulation using a commercially available generator and electrode system (Neurocybernetic Prosthesis System, NCP).

MATERIAL AND METHODS

During NCP implantation we recorded compound action potentials evoked by stimulating the left vagus nerve through the NCP bipolar lead. Current intensities were varied from 0.25 to 3.0 mA.

RESULTS

Vagus nerve compound action potential components conducting in the A, Adelta, and C velocity ranges could be elicited using either the NCP pulse generator or by a standard evoked potential instrument. A fiber potentials were recordable in all nerves, and were activated by very low stimulus currents. Adelta and C fibers were less reliably elicited, with C fibers requiring the highest currents.

CONCLUSIONS

Three clearly identified fiber populations can be identified using therapeutic electrical stimulation of the human vagus. Intraoperative measurements of NCP-induced action potentials may potentially provide a marker for therapeutic stimulation and better insight into mechanisms of vagus nerve stimulation (VNS) efficacy.

Pharmacologic evidence for a parasympathetic role in seizure-induced neurocardiac regulatory abnormalities

PURPOSE

We evaluated whether postictal cardiac arrhythmia can be prevented by pharmacologic blockage of peripheral muscarinic receptors in an experimental model of epilepsy in rats.

METHODS

Rats were prepared for chronic electrocardiograph recording and pretreated with atropine methyl bromide (2 or 10mg/kg i.p.) or saline prior to exposure to maximal electroshock (MES). The resulting seizure severity and duration of cardiac arrhythmia were measured.

RESULTS

Atropine methyl bromide did not significantly affect seizure severity in comparison to control animals but reduced the arrhythmia at a dose of 2mg/kg, and completely suppressed arrhythmia at 10mg/kg.

CONCLUSIONS

Postictal arrhythmia following MES-induced seizures may be blocked by pretreatment with atropine methyl bromide, a peripherally acting parasympatholytic agent. Our findings support previous observations that suggest strong participation of the parasympathetic system in postictal arrhythmia. This may be important for clinical suppression of cardiac arrhythmia in persons with uncontrolled epilepsy, who are at risk for sudden unexpected death.

The effect of vagus nerve stimulation on migraines

Vagus nerve stimulation (VNS) inhibits nociceptive behavior in animals. VNS might reduce pain in patients with VNS device implanted for intractable seizures. One case report described possible benefits on migraines. We contacted all patients who received VNS therapy for intractable epilepsy between 1993 and 1999 at Southern Illinois University, Springfield, Illinois. Patients who had concomitant chronic pain were subsequently interviewed. Pain intensity before and after VNS implantation was rated by the patient as average, worst, and least and on numeric rating scale from 1 to 10. Current pain measurements were compared to preimplantation by using Global Pain Relief Rating Scale. Of 62 patients who received VNS, 27 patients were interviewed; 4 patients had common migraine, and no other chronic pain syndromes were identified. All patients with migraine reported reductions in headache frequency and numeric rating scale score for average and least headache intensity. One patient reported complete relief of headaches. Improvement was reported to start 1 to 3 months after initiation of therapy. On Global Pain Relief Rating Scale, 1 patient reported complete pain relief, 2 reported a lot of pain relief, and 1 reported slight pain relief. Concomitant antiepileptic drugs were decreased in 3 patients and slightly increased in 1. VNS might be beneficial for prophylactic therapy of migraine.

Effects of seizure repetition on postictal and interictal neurocardiac regulation in the rat

PURPOSE

Human epilepsy is associated with abnormalities in cardiac regulation, as measured by reductions of heart rate variability (HRV) and approximate entropy (ApEn), but it is not known how these abnormalities are related to seizure experience.

METHODS

Baseline electrocardiogram (ECG) was recorded from seizure-naive rats. They were subjected daily to maximal electroshock (MES), which induced tonic seizures with hindlimb extension, for a total of 10 days. ECG was obtained for 30 min before and after the first and last seizure. R-R variability, spectral variability, and ApEn were calculated to determine changes in pre- and postictal cardiac regulation. Before the last seizure, interictal parameters were compared with baseline values to determine changes in interictal HRV as a consequence of seizure repetition. Postictal values obtained after the last seizure were compared with the initial postictal data to look for changes in postictal cardiac regulation.

RESULTS

During the postictal state, a mild, but significant, loss of ApEn was present after either the first or last seizure. Seizure repetition induced loss of R-R variability and high-frequency spectral band, which was present both interictally and postictally.

CONCLUSIONS

The results suggest that convulsive seizures are associated with an immediate reduction of the complexity of cardiac rhythm regulation, as reflected by reductions of ApEn. Seizure repetition may induce long-term neural abnormalities in neurocardiac regulatory systems, especially parasympathetic, which limit appropriate autonomic responses. These acquired abnormalities may, in turn, predispose individuals to cardiac arrhythmia and sudden unexpected death in epilepsy.

Effects of seizure severity and seizure repetition on postictal cardiac arrhythmia following maximal electroshock

Convulsive seizures triggered by maximal electroshock (MES) induce profound abnormalities in neural regulation of cardiac rhythm that are manifested by a period of marked cardiac arrhythmia in the immediate postictal state. It is not known whether seizure severity or seizure experience may influence the duration of cardiac arrhythmia in the postictal state. We varied the duration of MES administered to rats to vary seizure severity, as measured by the extensor to flexion (E/F) ratio. In separate experiments, rats were subjected to daily MES. Finally, we pretreated rats with ketamine prior to MES to block seizures hindlimb extension. In all animals, the R-R interval was plotted on the tachogram, and the duration of the arrhythmia was measured. Increases in MES duration increased significantly the E/F ratio and prolonged significantly the postictal cardiac arrhythmia. Repetition of MES caused a kindling effect with respect to seizure severity resulting in a significant increase of the E/F ratio and significant increases in the duration of postictal arrhythmia. Blocking of the hindlimb extension by ketamine abolished arrhythmia suggesting that the arrhythmia is not caused directly by MES. Severity of tonic convulsive seizures is a determinant of disordered cardiac autonomic regulation and directly influences the duration of cardiac arrhythmia during the immediate postictal state following MES. Seizure repetition also increases abnormalities of postictal neural regulation of the heart, but further studies are needed to determine whether this effect is independent of seizure severity increases.

Safety and tolerance of rapidly infused Depacon. A randomized trial in subjects with epilepsy

BACKGROUND

Valproate sodium injection (Depacon(R)) is an intravenous form of valproate for use in absence and complex partial seizures when circumstances preclude oral administration. Certain situations may warrant larger and more rapid infusions than permitted by the original labeling. This study evaluated the safety of more rapid infusions.

METHODS

Subjects with epilepsy were randomized in a 2:1 ratio to receive up to 15 mg/kg of valproate sodium infused at 3.0 or 1.5 mg/kg/min. Up to four infusions were allowed within 24 h to achieve target plasma valproate concentrations of 50-100 mcg/ml. Primary safety endpoints were the changes in the 5-min and minimum post-first infusion blood pressures (BPs).

RESULTS

One hundred twelve subjects were treated, (3.0 mg/kg/min group: n=72, 1.5 mg/kg/min group: n=40). No significant treatment differences were detected for changes in the primary BP endpoints. Two subjects in the 3.0 mg/kg/min group had potentially clinically significant low systolic BP values during the study. Similar proportions of subjects in the two groups reported adverse events during or within 6 h following the first infusion.

CONCLUSIONS

Valproate sodium injection dosages up to 15 mg/kg and rates of 1.5 and 3.0 mg/kg/min were well tolerated in this population.

Self-inflicted vocal cord paralysis in patients with vagus nerve stimulators. Report of two cases

Vagus nerve stimulation for treatment of epilepsy is considered safe; reports of severe complications are rare. The authors report on two developmentally disabled patients who experienced vocal cord paralysis weeks after placement of a vagus nerve stimulator. In both cases, traction injury to the vagus nerve resulting in vocal cord paralysis was caused by rotation of the pulse generator at the subclavicular pocket by the patient. Traumatic vagus nerve injury caused by patients tampering with their device has never been reported and may be analogous to a similar phenomenon reported for cardiac pacemakers in the literature. As the use of vagus nerve stimulation becomes widespread it is important to consider the potential for this adverse event.

Cardiac dysrhythmia associated with the immediate postictal state after maximal electroshock in freely moving rat

PURPOSE

Cardiac autonomic changes accompany complex partial seizures and generalized tonic-clonic seizures, and participate, at least partially, in the sudden and unexpected death in epilepsy (SUDEP). The analysis of the heart rate variability (HRV) is one of the simplest ways of providing insight into autonomic functions. The entropy quantifies the repetition of complex patterns in a signal and refers to systems randomness, regularity, and predictability. Clinical investigations have reported that entropy decreases in patients with a high risk of sudden cardiac death. The goal of this study was to evaluate the effects of the maximal electroshock (MES) on the entropy of HRV, monitored in the immediate postictal stage in the model of the freely moving rat.

METHODS

Entropy changes were correlated with the high and low frequencies of spectral analysis, which reflect the participation of the sympathetic and parasympathetic activities.

RESULTS

MES-induced arrhythmia is characterized by an HRV increase, an imbalance in favor of the parasympathetic activity, and a decrease in the entropy. Entropy decrease was restricted to the duration of the arrhythmia, suggesting that the postictal arrhythmia may be associated with a higher risk of lethal cardiac complications. Nevertheless, entropy changes did not correlate with spectral changes.

CONCLUSIONS

The results suggest that the imbalance demonstrated in the spectral domain explains only partially the contribution of each autonomic system in the complexity of the heart rate during the postictal state.

Modulation of audiogenically kindled seizures by gamma-aminobutyric acid-related mechanisms in the amygdala

Repetitive induction of audiogenic seizures (AGSs) ("AGS kindling") results in expansion of the AGS neuronal network from the brainstem to forebrain structures. AGSs in kindled genetically epilepsy-prone rats (GEPR-9s) exhibit a significant increase in the duration of posttonic clonus (PTC). The amygdala (AMG) does not appear to be a required network component before AGS kindling, but this structure is implicated in the seizure network after AGS kindling. gamma-Aminobutyric acid (GABA) is a major neurotransmitter in AMG, and histamine receptor activation is also reported to stimulate GABA release. The present study examined the effect on audiogenically kindled seizures of focal microinjections into the AMG of GEPR-9s. AGS kindling involved induction of 14 AGSs in GEPR-9s. Bilateral microinjection of a GABA(A) agonist, muscimol (0.3 nmol/side), into the AMG significantly reduced the duration of PTC, starting 0.5 h after drug infusion, with recovery by 24 h. Microinjection of histamine (60 nmol/side) suppressed PTC at 0.5 h, with total blockade at 24 h, but the seizure pattern did not revert to that observed before kindling until 120 h. This long duration suggests that mechanisms in addition to modulation of GABA function may be involved in the effect of histamine. The wild running and tonic components of AGS were never affected by microinjection of these agents into the AMG. These findings confirm previous work suggesting that the AMG is not a required nucleus in the AGS neuronal network before kindling. However, the AMG becomes critical in expansion of the seizure network during AGS kindling, and audiogenically kindled seizures are negatively modulated by increased GABA function.

Intravenous valproate is well tolerated in unstable patients with status epilepticus

The authors reviewed hospital records of 13 patients with status epilepticus and hypotension who received IV valproate therapy. Most patients were elderly (74.4 +/- 12.5 [SD] years) and received a loading dose of valproate of 25.1 +/- 5.0 mg/kg (range 14.7 to 32.7), at a rate of 36.6 +/- 25.1 mg/min (range 6.3 to 100). There were no significant changes in blood pressure, pulse, or use of vasopressors. The data suggest that valproate loading is well tolerated, even in patients with cardiovascular instability.

Prospective long-term study of vagus nerve stimulation for the treatment of refractory seizures

PURPOSE

To determine the long-term efficacy of vagus nerve stimulation (VNS) for refractory seizures. VNS is a new treatment for refractory epilepsy. Two short-term double-blind trials have demonstrated its safety and efficacy, and one long-term study in 114 patients has demonstrated a cumulative improvement in efficacy at 1 year. We report the largest prospective long-term study of VNS to date.

METHODS

Patients with six or more complex partial or generalized tonic-clonic seizures enrolled in the pivotal EO5 study were prospectively evaluated for 12 months. The primary outcome variable was the percentage reduction in total seizure frequency at 3 and 12 months after completion of the acute EO5 trial, compared with the preimplantation baseline. Subjects originally randomized to low stimulation (active-control group) were crossed over to therapeutic stimulation settings for the first time. Subjects initially randomized to high settings were maintained on high settings throughout the 12-month study.

RESULTS

The median reduction at 12 months after completion of the initial double-blind study was 45%. At 12 months, 35% of 195 subjects had a >50% reduction in seizures, and 20% of 195 had a >75% reduction in seizures.

CONCLUSIONS

The efficacy of VNS improves during 12 months, and many subjects sustain >75% reductions in seizures.

Prolongation of midazolam half-life after sustained infusion for status epilepticus

Midazolam clearance was examined in two patients with medically refractory convulsive status epilepticus. One patient received a constant infusion of midazolam for 68 hours and the other patient received a constant infusion of midazolam for 148 hours. In both patients the decline in level was, overall, much slower than expected. The half-lives of the terminal phase were longer than typically published (52.9 hours in Patient 1 and 20.1 hours in Patient 2). Thus, the data suggest that midazolam exhibits use-dependent pharmacokinetic changes that may be important clinically in situations that require prolonged midazolam therapy.

Age-related changes in GABA(A) receptor subunit composition and function in rat auditory system

A decline in the ability to discriminate speech from noise due to age-related hearing loss (presbycusis) may reflect impaired auditory information processing within the central nervous system. Presbycusis may result, in part, from functional loss of the inhibitory neurotransmitter GABA. The present study assessed age-related changes of the GABA(A) receptor in the inferior colliculus of young-adult, middle-aged, and aged rats related to: (i) receptor subunit composition and (ii) receptor function. Western blotting was used to measure protein levels of selected GABA(A) receptor subunits in preparations obtained from the inferior colliculus of Fischer 344 and Fischer 344/Brown-Norway F1 hybrid rats. In both strains, the aged group exhibited significant increases in gamma1 subunit protein and a decrease in alpha1 subunit protein. To examine the functional consequence of this putative age-related subunit change, we measured the ability of exogenous GABA to flux/translocate chloride ions into microsac preparations derived from Fischer 344 inferior colliculus. GABA-mediated chloride influx was significantly increased in samples prepared from the inferior colliculus of aged animals. Together with previous studies, these results strongly suggest an age-related change in GABA(A) receptor composition. These changes may reflect a compensatory up-regulation of inhibitory function in the face of significant loss of presynaptic GABA release. These findings provide one example of plastic neurotransmitter receptor changes which can occur during the ageing process.

Revision and removal of stimulating electrodes following long-term therapy with the vagus nerve stimulator

BACKGROUND

A significant concern about vagus nerve stimulation therapy has been the disposition of the spiral stimulating electrodes once treatment is considered ineffective or is no longer desired. Because the electrodes are wrapped around the vagus nerve, there is the potential for nerve injury during their removal.

METHODS

We attempted removal of the spiral stimulating electrodes from 10 patients who received long-term vagus nerve stimulation therapy for drug-resistant epilepsy. In some patients, replacement with electrodes was also performed for poorly functioning leads.

RESULTS

The mean duration of electrode implantation was 3.7+/-2.2 years (range 1.1-7.3 years). In seven patients, the old electrodes were removed completely from the nerve. No adverse events occurred intraoperatively or postoperatively.

CONCLUSIONS

Our results indicate that the spiral electrodes may be safely removed from the vagus nerve, even after the electrodes have been implanted for several years. The reversibility of lead implantation may enhance the attractiveness of vagus nerve stimulation therapy for patients with medically-intractable epilepsy.

Intravenous loading of valproate for epilepsy

Valproate is an antiepileptic drug that has broad spectrum activity against several types of seizure. Little information is available about the use of valproate for acute loading of patients when a rapid increase in serum level is needed. We describe the use of intravenous valproate in 20 adults with epilepsy. In each case, a loading dose was calculated by multiplying the patient's body mass, desired change in serum level, and estimated volume of distribution. The mean dose (+/- SD) administered was 1420 +/- 440 mg (19.4 +/- 5.4 mg/kg). In four patients, the dose was infused at 20 mg/min; in all other patients, infusions were performed at 50 mg/min. The infusions were tolerated well and few clinical side effects were observed. Postinfusion levels were drawn and the apparent volume of distribution was calculated to be 0.22 +/- 0.04 L/kg. The results indicate that intravenous valproate may be used to quickly and efficiently increase serum levels in patients with epilepsy.

Enhanced recognition memory following vagus nerve stimulation in human subjects

Neuromodulators associated with arousal modulate learning and memory, but most of these substances do not freely enter the brain from the periphery. In rodents, these neuromodulators act in part by initiating neural messages that travel via the vagus nerve to the brain, and electrical stimulation of the vagus enhances memory. We now extend that finding to human verbal learning. We examined word-recognition memory in patients enrolled in a clinical study evaluating the capacity of vagus nerve stimulation to control epilepsy. Stimulation administered after learning significantly enhanced retention. These findings confirm in humans the hypothesis that vagus nerve activation modulates memory formation similarly to arousal.

Posttraining electrical stimulation of vagal afferents with concomitant vagal efferent inactivation enhances memory storage processes in the rat

Peripherally administered or released substances that modulate memory storage, but do not freely enter the brain, may produce their effects on memory by activating peripheral receptors that send messages centrally through the vagus nerve. Indeed, vagus nerve stimulation enhances memory performance, although it is unclear whether this effect is due to the activation of vagal afferents or efferents. To eliminate the possible influence of descending fibers on memory storage processes, rats were implanted with cuff electrode/catheter systems along the left cervical vagus. Forty-eight hours following surgery, each animal received a 3. 0-microliter infusion (1.0 microliter/min) of either lidocaine hydrochloride (75.0 mM) or isotonic saline below the point of stimulation. Animals were then trained 10 min later on an inhibitory-avoidance task with a 0.75-mA, 1.0-s foot shock. Sham stimulation or vagus nerve stimulation (0.5-ms biphasic pulses; 20.0 Hz; 30 s; 0.2, 0.4, or 0.8 mA) was administered immediately after training. Memory, tested 24 h later, was enhanced by stimulation whether descending vagus nerve fibers were inactivated or not. Both lidocaine- and saline-infused groups showed an intensity-dependent, inverted-U-shaped pattern of retention performance, with the greatest effect observed for 0.4 mA (U = 9, p < .05, and U = 7, p < .01, respectively). Additionally, animals that received lidocaine infusions, but no vagus nerve stimulation, showed impaired memory compared to the performance of saline-infused control animals (U = 11, p < .05). Together, these findings suggest that vagal afferents carry messages about peripheral states that lead to the modulation of memory storage and that the memory-enhancing effect produced by vagus nerve stimulation is not mediated via the activation of vagal efferents.

Vagus nerve stimulation therapy for partial-onset seizures: a randomized active-control trial

OBJECTIVE

The purpose of this multicenter, add-on, double-blind, randomized, active-control study was to compare the efficacy and safety of presumably therapeutic (high) vagus nerve stimulation with less (low) stimulation.

BACKGROUND

Chronic intermittent left vagus nerve stimulation has been shown in animal models and in preliminary clinical trials to suppress the occurrence of seizures.

METHODS

Patients had at least six partial-onset seizures over 30 days involving complex partial or secondarily generalized seizures. Concurrent antiepileptic drugs were unaltered. After a 3-month baseline, patients were surgically implanted with stimulating leads coiled around the left vagus nerve and connected to an infraclavicular subcutaneous programmable pacemaker-like generator. After randomization, device initiation, and a 2-week ramp-up period, patients were assessed for seizure counts and safety over 3 months. The primary efficacy variable was the percentage change in total seizure frequency compared with baseline.

RESULTS

Patients receiving high stimulation (94 patients, ages 13 to 54 years) had an average 28% reduction in total seizure frequency compared with a 15% reduction in the low stimulation group (102 patients, ages 15 to 60 year; p = 0.04). The high-stimulation group also had greater improvements on global evaluation scores, as rated by a blinded interviewer and the patient. High stimulation was associated with more voice alteration and dyspnea. No changes in physiologic indicators of gastric, cardiac, or pulmonary functions occurred.

CONCLUSIONS

Vagus nerve stimulation is an effective and safe adjunctive treatment for patients with refractory partial-onset seizures. It represents the advent of a new, nonpharmacologic treatment for epilepsy.

Antidepressants and seizures: clinical anecdotes overshadow neuroscience

Pharmacological treatment of depression in persons with epilepsy has been an area of controversy because some drugs commonly are perceived specifically to induce or exacerbate seizures in patients with seizure disorders. This prevailing misconception is unjustified by scientific studies, yet it continues to prevent afflicted persons from receiving appropriate therapy. The scientific literature shows that tricyclic antidepressant drugs cause seizures in overdose in both animals and humans. In lower doses, these drugs have anticonvulsant activity in humans and animals. Thus, the antidepressant drugs are like several antiepileptic drugs that can both prevent and cause seizures. The anticonvulsant activity of antidepressant drugs has been studied extensively in animals and almost certainly stems from their capacity to block norepinephrine and/or serotonin reuptake. The pharmacodynamic action responsible for their convulsant effects has not been well studied but may be due to their local anesthetic, antihistaminic, or antimuscarinic activity. The newer, more selective monoamine uptake blockers have very low convulsant liability, and it is suggested that their anticonvulsant activity, which is well documented in animals, be investigated further in humans. If their effects in humans are analogous to those in animals, these drugs can be used safely in epileptic patients with depression, and it is possible that their anticonvulsant activity can be exploited for use in the treatment of epilepsy.

Vagus nerve stimulation induces a sustained anticonvulsant effect

PURPOSE

Stimulation of the vagus nerve can effectively abort several types of experimentally induced seizures in animals when administered near the time of seizure onset. Indirect evidence from human trials and animal studies suggests that the anticonvulsant effects of vagus nerve stimulation (VNS) extend beyond the duration of stimulation. We used the pentylenetetrazol model to determine whether VNS exerts a persistent anticonvulsant effect.

METHODS

VNS (1 mA, 30 Hz, 500 microseconds pulse width) was administered continuously for 0.1, or 60 min, or intermittently (30 s on, 5 min off) for 60 min, to awake and freely moving animals. After the end of stimulation, pentylenetetrazol (50 mg/kg i.p.) was administered to induce seizures. Time-course studies were also performed, consisting of 60 min of VNS followed by pentylenetetrazol injection after 0, 3-, 5-, and 10-min intervals.

RESULTS

The greatest anticonvulsant effect occurred after 60 min of continuous VNS, which prevented convulsions in four of 12 rats and reduced significantly seizure duration, the total number of seizures, and number of tonic seizures. Intermittent VNS was less effective than continuous stimulation for 60 min, but more effective than that for 1 min. The anticonvulsant effect declined in a time-dependent fashion after discontinuation of VNS, with return to nonstimulated control values by 10 min.

CONCLUSIONS

The results of this study verify a persistent VNS-induced anticonvulsant effect and indicate that its efficacy is dependent on the cumulative stimulus duration.

Gabapentin for the treatment of hemifacial spasm

Pharmacologic therapy for hemifacial spasm is often limited by the paucity of effective medications and problems with side effects. Gabapentin is a novel antiepileptic drug that is generally well tolerated. Its anticonvulsant effect is independent of gamma-aminobenzoic acid (GABA) receptor mechanisms. We report a patient with hemifacial spasm who responded well to gabapentin therapy. Gabapentin may be a useful alternative medical therapy to currently used drugs.

Onset of neurologic deficits after treatment with dihydroergotamine in a patient with sagittal sinus thrombosis

A woman with a 7-year history of intermittent migraine had 3 months of gradually worsening headaches. Initial neurologic examination including fundus examination was normal, and initial head computerized tomographic (CT) scan and magnetic resonance imaging (MRI) were thought to be normal. The patient was given dihydroergotamine (DHE-45), 1.0 mg, intravenously for relief of headache. Five hours later, she complained of severe diffuse headache and nausea. Neurologic examination showed left arm weakness and sensory loss, blurring of the left optic disc, and bilateral Babinski signs. Cerebral arteriography demonstrated thrombosis of the sagittal sinus, which in retrospect was present on the initial contrast CT scan and MRI scan. The patient's deficits worsened, and she eventually died 20 days later as a result of cerebral infarctions and increased intracranial pressure, despite attempts at selective thrombolysis of the sagittal sinus. DHE has potent venoconstrictive effects. We suspect that DHE helped precipitate neurologic deterioration in this patient with sagittal sinus thrombosis.

Regional induction of fos immunoreactivity in the brain by anticonvulsant stimulation of the vagus nerve

Electrical stimulation of the vagus nerve exerts an antiepileptic effect on human partial-onset epilepsy, but little is known about the brain structures that mediate this phenomenon. Fos is a nuclear protein that is expressed under conditions of high neuronal activity. We utilized fos immunolabeling techniques on Sprague-Dawley rat brains to identify regions that are activated by antiepileptic stimulation of the left vagus nerve. Vagus nerve stimulation (VNS) induced specific nuclear fos immunolabeling in several forebrain structures, including the posterior cortical amygdaloid nucleus, cingulate and retrosplenial cortex, ventromedial and arcuate hypothalamic nuclei. In the brainstem, there was specific immunolabeling in vagus nerve nuclei, in the A5 and locus ceruleus noradrenergic nuclei, and in the cochlear nucleus. No labeling of these structures occurred in sham-operated, unstimulated control animals. Intense labeling also occurred in habenular nucleus of thalamus after vagus nerve stimulation, whereas only mild staining occurred in unstimulated animals. Several of the brain structures activated by VNS are important for genesis or regulation of seizures in the forebrain. These structures may mediate the antiepileptic effect of VNS.

Noncompetitive and competitive NMDA antagonists exert anticonvulsant effects by actions on different sites within the neuronal network for audiogenic seizures

Excitant amino acids are implicated in audiogenic seizure (AGS) susceptibility in the genetically epilepsy-prone rat (GEPR). In the present study systemic administration of NMDA receptor antagonists significantly decreased AGS severity in the GEPR. Systemic administration of the competitive NMDA antagonists 3-((+-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP) and 2-amino-7-phosphonoheptanoic acid and the non-competitive antagonist dizocilpine (MK-801) were effectively anticonvulsant in the GEPR. The inferior colliculus is the most critical nucleus for AGS initiation in the GEPR and an excitant amino acid is implicated as an important excitatory transmitter in inferior colliculus neurons. Systemically administered CPP significantly reduced inferior colliculus neuronal firing in the normal behaving rat and the GEPR concurrently with blockade of AGS and this effect occurred at nearly all sound intensities tested. Systemic administration of MK-801, while effective in blocking AGS, produced no consistent change in inferior colliculus neuronal firing, which is consistent with its very low potency in blocking AGS with bilateral microinjection into the inferior colliculus. These findings suggest that an important action of competitive, but not noncompetitive, NMDA antagonists is on brain stem auditory nuclei, especially the inferior colliculus, that are critical to AGS. MK-801 appears to exert its anticonvulsant effects in AGS network sites beyond the inferior colliculus. These findings and recent inferior colliculus slice studies suggest that NMDA receptors in inferior colliculus may have quantitatively different properties from those in other brain regions. These differences in NMDA receptor function in inferior colliculus may reflect NMDA receptor heterogeneity observed in binding studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Glutamate in the inferior colliculus plays a critical role in audiogenic seizure initiation

Alterations of excitant amino acid (EAA) action are implicated in seizure susceptibility in the genetically epilepsy-prone rat (GEPR). The inferior colliculus (IC) is critical for audiogenic seizure (AGS) initiation in the GEPR. The present study observed that bilateral microinjection into the IC of L-canaline, a glutamate synthesis inhibitor, decreased AGS severity in the GEPR and also decreased potassium-evoked release of glutamate from IC slices. Bilateral microinjection of NMDA receptor antagonists, 2-amino-7-phosphonoheptanoate (AP7) or 3-((+/-)-2-carboxypiperazin-4-yl)-propyl-1-phosphonate (CPP) into IC blocked AGS, and an antagonist at non-NMDA EAA receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), also blocked AGS. NMDA receptor antagonists were 5-200 times more effective than CNQX. Microinjection of a non-competitive NMDA receptor antagonist, dizocilpine (MK-801), into IC had little effect except with very high doses. Microinjection of CPP or AP7 into the IC blocked AGS at considerably lower doses as compared to pontine reticular formation (PRF). However, MK-801 attenuated AGS when microinjected into PRF at doses that were ineffective in IC. Systemically administered CPP blocked AGS and significantly reduced IC neuronal firing in the behaving GEPR, suggesting an important action of systemically administered NMDA receptor antagonists on brainstem auditory nuclei critical to AGS. The present results support a critical role for glutamate acting, in part, through NMDA receptors in IC in initiation of AGS.

Chronic vagus nerve stimulation increases the latency of the thalamocortical somatosensory evoked potential

The Neurocybernetic Prosthesis (NCP) is a pacemaker-like device that has been designed to provide chronic intermittent vagus nerve stimulation. It is currently under study for the treatment of refractory partial onset epilepsy, and preliminary studies have indicated that partial onset seizures are improved by this therapy. The mechanisms by which it exerts its antiepileptic effect are not well understood. Although there are extensive pathways to the forebrain from the nuclei of the vagus nerve, the evidence that the NCP alters neural transmission outside the vagal system is limited. We prospectively examined somatosensory and brain stem auditory evoked potentials (BAEPs) in three patients receiving NCP implantation to determine if changes in these studies occur as a result of chronic vagus nerve stimulation. The results demonstrate a significant prolongation of the cervicomedullary to thalamocortical potential (N13-N20) interval on somatosensory evoked potential (SSEP) studies following activation of the device. No other significant changes were seen on SSEP or BAEP in the NCP implanted patients or normal controls. The findings suggest that chronic vagus nerve stimulation does alter neuronal networks outside of the brain stem vagus system, and may potentially provide a means to clinically monitor and titrate this therapy.

Repetition of audiogenic seizures in genetically epilepsy-prone rats induces cortical epileptiform activity and additional seizure behaviors

Repetition of seizures appears to increase severity in a number of seizure models, but the nature of these severity increases has not been elucidated in naturally occurring genetic epilepsy models. The genetically epilepsy-prone rat (GEPR) is highly susceptible to many seizure provoking stimuli, and high intensity acoustic stimuli induce audiogenic seizures (AGS). The role of forebrain structures in AGS in the GEPR has not been clear, and the presence of cortical epileptiform EEG activity in the GEPR is controversial. The present study examined the effects of 21 daily AGS repetitions on behavior and EEG activity recorded from the cortex of two GEPR substrains that exhibit moderate (GEPR-3) or severe AGS (GEPR-9). The results indicated that AGS repetition induced seizure severity increases in both GEPR substrains and resulted in prominent cortical epileptiform EEG activity. The AGS behavioral patterns remained distinctly different in the two substrains throughout seizure repetition. In each substrain a different additional behavioral phase was expressed; the GEPR-9 exhibited post-tonic clonus, and the GEPR-3 exhibited facial and forelimb clonus. These findings indicate that seizure repetition results in expansion of the neuronal network subserving AGS to involve forebrain structures. The medial geniculate body and amygdala appear to be part of this expanded network, and long-term potentiation, which was reported in the pathway between the latter brain structures, may be involved. These data suggest that recruitment of forebrain structures into the AGS neuronal network appears to be essential for production of the additional ictal behaviors evoked by AGS repetition.

Convulsant and anticonvulsant cyclopentanones and cyclohexanones

The convulsant and/or anticonvulsant activity of unsubstituted and mono-alkyl-substituted cyclopentanones and cyclohexanones were examined by testing the ability of these compounds to produce seizures or to inhibit seizures induced by pentylenetetrazol and maximal electroshock in CF-1 mice. In addition, these compounds were tested for their ability to bind to the picrotoxin receptor. The unsubstituted compounds, cyclopentanone and cyclohexanone, prevented both pentylnetetrazol- and maximal electroshock-induced seizures. Cyclopentanones and cyclohexanones with small (less than 3 carbon atoms) alkyl substituents in the 2-position were also anticonvulsant; all of these compounds, except 2-ethylcyclohexanone, blocked both pentylenetrazol- and maximal electroshock-induced seizures. 2-Ethylcyclohexanone was very effective against pentylenetetrazol seizures but did not prevent maximal electroshock seizures. Cyclohexanones with larger alkyl substituents in the 2-position, 2-propylcyclohexanone and 2-t-butylcyclohexanone, caused clonic seizures following injection into mice. Of the cyclopentanones and cyclohexanones with alkyl substitutions in the 3-position that were studied, one was an anticonvulsant (3-methylcyclopentanone), one was a mixed convulsant/anticonvulsant (3-ethylcyclohexanone), and the other two (3-ethylcyclopentanone and 3-t-butylcyclohexanone) were convulsants. Finally, two cyclohexanones with alkyl substituents in the 4-position were studied. Both 4-ethylcyclohexanone and 4-t-butylcyclohexanone produced convulsions when injected into mice. All the neuroactive cyclopentanones and cyclohexanones competitively displaced [35S]t-butylbicyclophosphorothionate, a ligand specific for the picrotoxin receptor, from rat brain membranes. The convulsant compounds were generally more potent than the anticonvulsants. The cyclohexanones were more potent than their corresponding cyclopentanones and the binding potency of both increased as the size of the alkyl substituent increased. These results suggest that cyclopentanone, cyclohexanone, and their alkyl-substituted derivatives act at the picrotoxin receptor to increase or decrease neuronal activity. Thus, they appear to have sites and mechanisms of action similar to those of the neuroactive gamma-butyrolactones and gamma-thiobutyrolactones.